From 05fed879afada2f6ac1f1b5b6962e06190f5b9f6 Mon Sep 17 00:00:00 2001
From: Tony Cook <tony@develop-help.com>
Date: Mon, 25 Mar 2019 16:11:16 +1100
Subject: [PATCH] (perl #133951) don't write an invalid lib/buildcustomize.pl

Cwd under miniperl (at this point) can't determine the current
directory if some ancestor directory isn't readable.

So Cwd::getcwd() would return undef, and write_buildcustomize.pl
would write out a list of paths relative to / rather than to the cwd.
--- write_buildcustomize.pl
+++ write_buildcustomize.pl
@@ -61,6 +61,9 @@
 
 my $cwd  = Cwd::getcwd();
 
+defined $cwd
+  or die "$0: Can't determine current working directory\n";
+
 # lib must be last, as the toolchain modules write themselves into it
 # as they build, and it's important that @INC order ensures that the partially
 # written files are always masked by the complete versions.